package wiget;

/**
 * Created by Administrator on 2017/7/13.
 */

import java.util.LinkedList;
import java.util.Queue;

import android.content.Context;
import android.database.DataSetObserver;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.GestureDetector.OnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.Scroller;

public class HorizontalListView extends AdapterView<ListAdapter>
{

    public boolean mAlwaysOverrideTouch = true;

    protected ListAdapter mAdapter;

    private int mLeftViewIndex = -1;

    private int mRightViewIndex = 0;

    protected int mCurrentX;

    protected int mNextX;

    private int mMaxX = Integer.MAX_VALUE;

    private int mDisplayOffset = 0;

    protected Scroller mScroller;

    private GestureDetector mGesture;

    private Queue<View> mRemovedViewQueue = new LinkedList<View>();

    private OnItemSelectedListener mOnItemSelected;

    private OnItemClickListener mOnItemClicked;

    private OnItemLongClickListener mOnItemLongClicked;

    private boolean mDataChanged = false;

    public HorizontalListView(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        initView();
    }

    private synchronized void initView()
    {
        mLeftViewIndex = -1;
        mRightViewIndex = 0;
        mDisplayOffset = 0;
        mCurrentX = 0;
        mNextX = 0;
        mMaxX = Integer.MAX_VALUE;
        mScroller = new Scroller(getContext());
        mGesture = new GestureDetector(getContext(), mOnGesture);
    }

    @Override
    public void setOnItemSelectedListener(AdapterView.OnItemSelectedListener listener)
    {
        mOnItemSelected = listener;
    }

    @Override
    public void setOnItemClickListener(AdapterView.OnItemClickListener listener)
    {
        mOnItemClicked = listener;
    }

    @Override
    public void setOnItemLongClickListener(AdapterView.OnItemLongClickListener listener)
    {
        mOnItemLongClicked = listener;
    }

    private DataSetObserver mDataObserver = new DataSetObserver()
    {

        @Override
        public void onChanged()
        {
            synchronized (HorizontalListView.this)
            {
                mDataChanged = true;
            }
            invalidate();
            requestLayout();
        }

        @Override
        public void onInvalidated()
        {
            reset();
            invalidate();
            requestLayout();
        }

    };

    @Override
    public ListAdapter getAdapter()
    {
        return mAdapter;
    }

    @Override
    public View getSelectedView()
    {
        // TODO: implement
        return null;
    }

    @Override
    public void setAdapter(ListAdapter adapter)
    {
        if (mAdapter != null)
        {
            mAdapter.unregisterDataSetObserver(mDataObserver);
        }
        mAdapter = adapter;
        mAdapter.registerDataSetObserver(mDataObserver);
        reset();
    }

    private synchronized void reset()
    {
        initView();
        removeAllViewsInLayout();
        requestLayout();
    }

    @Override
    public void setSelection(int position)
    {
        //
    }

    public void scrollToRight()
    {
        if (mAdapter == null)
        {
            return;
        }
        System.out.println("myth" + mNextX);
        mNextX = mMaxX;
        System.out.println("myth" + mNextX);
        requestLayout();
    }

    private void addAndMeasureChild(final View child, int viewPos)
    {
        LayoutParams params = child.getLayoutParams();
        if (params == null)
        {
            params = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
        }

        addViewInLayout(child, viewPos, params, true);
        child.measure(MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.AT_MOST),
                MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.AT_MOST));
    }

    @Override
    protected synchronized void onLayout(boolean changed, int left, int top, int right, int bottom)
    {
        super.onLayout(changed, left, top, right, bottom);

        if (mAdapter == null)
        {
            return;
        }

        if (mDataChanged)
        {
            int oldCurrentX = mCurrentX;
            initView();
            removeAllViewsInLayout();
            mNextX = oldCurrentX;
            mDataChanged = false;
        }

        if (mScroller.computeScrollOffset())
        {
            int scrollx = mScroller.getCurrX();
            mNextX = scrollx;
        }

        if (mNextX <= 0)
        {
            mNextX = 0;
            mScroller.forceFinished(true);
        }
        if (mNextX >= mMaxX)
        {
            mNextX = mMaxX;
            mScroller.forceFinished(true);
        }

        int dx = mCurrentX - mNextX;

        removeNonVisibleItems(dx);
        fillList(dx);
        positionItems(dx);

        mCurrentX = mNextX;

        if (!mScroller.isFinished())
        {
            post(new Runnable()
            {
                @Override
                public void run()
                {
                    requestLayout();
                }
            });

        }
    }

    private void fillList(final int dx)
    {
        int edge = 0;
        View child = getChildAt(getChildCount() - 1);
        if (child != null)
        {
            edge = child.getRight();
        }
        fillListRight(edge, dx);

        edge = 0;
        child = getChildAt(0);
        if (child != null)
        {
            edge = child.getLeft();
        }
        fillListLeft(edge, dx);

    }

    private void fillListRight(int rightEdge, final int dx)
    {
        while (rightEdge + dx < getWidth() && mRightViewIndex < mAdapter.getCount())
        {

            View child = mAdapter.getView(mRightViewIndex, mRemovedViewQueue.poll(), this);
            addAndMeasureChild(child, -1);
            rightEdge += child.getMeasuredWidth();

            if (mRightViewIndex == mAdapter.getCount() - 1)
            {
                mMaxX = mCurrentX + rightEdge - getWidth();
            }

            if (mMaxX < 0)
            {
                mMaxX = 0;
            }
            mRightViewIndex++;
        }

    }

    private void fillListLeft(int leftEdge, final int dx)
    {
        while (leftEdge + dx > 0 && mLeftViewIndex >= 0)
        {
            View child = mAdapter.getView(mLeftViewIndex, mRemovedViewQueue.poll(), this);
            addAndMeasureChild(child, 0);
            leftEdge -= child.getMeasuredWidth();
            mLeftViewIndex--;
            mDisplayOffset -= child.getMeasuredWidth();
        }
    }

    private void removeNonVisibleItems(final int dx)
    {
        View child = getChildAt(0);
        while (child != null && child.getRight() + dx <= 0)
        {
            mDisplayOffset += child.getMeasuredWidth();
            mRemovedViewQueue.offer(child);
            removeViewInLayout(child);
            mLeftViewIndex++;
            child = getChildAt(0);

        }

        child = getChildAt(getChildCount() - 1);
        while (child != null && child.getLeft() + dx >= getWidth())
        {
            mRemovedViewQueue.offer(child);
            removeViewInLayout(child);
            mRightViewIndex--;
            child = getChildAt(getChildCount() - 1);
        }
    }

    private void positionItems(final int dx)
    {
        if (getChildCount() > 0)
        {
            mDisplayOffset += dx;
            int left = mDisplayOffset;
            for (int i = 0; i < getChildCount(); i++)
            {
                View child = getChildAt(i);
                int childWidth = child.getMeasuredWidth();
                child.layout(left, 0, left + childWidth, child.getMeasuredHeight());
                left += childWidth + child.getPaddingRight();
            }
        }
    }

    public synchronized void scrollTo(int x)
    {
        mScroller.startScroll(mNextX, 0, x - mNextX, 0);
        requestLayout();
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev)
    {
        boolean handled = super.dispatchTouchEvent(ev);
        ;
        return handled | mGesture.onTouchEvent(ev);
    }

    protected boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
    {
        synchronized (HorizontalListView.this)
        {
            mScroller.fling(mNextX, 0, (int) -velocityX, 0, 0, mMaxX, 0, 0);
        }
        requestLayout();

        return true;
    }

    protected boolean onDown(MotionEvent e)
    {
        mScroller.forceFinished(true);
        return true;
    }

    private OnGestureListener mOnGesture = new GestureDetector.SimpleOnGestureListener()
    {

        @Override
        public boolean onDown(MotionEvent e)
        {
            return HorizontalListView.this.onDown(e);
        }

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
        {
            return HorizontalListView.this.onFling(e1, e2, velocityX, velocityY);
        }

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)
        {

            synchronized (HorizontalListView.this)
            {
                mNextX += (int) distanceX;
            }
            requestLayout();

            return true;
        }

        @Override
        public boolean onSingleTapConfirmed(MotionEvent e)
        {
            for (int i = 0; i < getChildCount(); i++)
            {
                View child = getChildAt(i);
                if (isEventWithinView(e, child))
                {
                    if (mOnItemClicked != null)
                    {
                        mOnItemClicked.onItemClick(HorizontalListView.this, child, mLeftViewIndex + 1 + i,
                                mAdapter.getItemId(mLeftViewIndex + 1 + i));
                    }
                    if (mOnItemSelected != null)
                    {
                        mOnItemSelected.onItemSelected(HorizontalListView.this, child, mLeftViewIndex + 1 + i,
                                mAdapter.getItemId(mLeftViewIndex + 1 + i));
                    }
                    break;
                }

            }
            return true;
        }

        @Override
        public void onLongPress(MotionEvent e)
        {
            int childCount = getChildCount();
            for (int i = 0; i < childCount; i++)
            {
                View child = getChildAt(i);
                if (isEventWithinView(e, child))
                {
                    if (mOnItemLongClicked != null)
                    {
                        mOnItemLongClicked.onItemLongClick(HorizontalListView.this, child, mLeftViewIndex + 1 + i,
                                mAdapter.getItemId(mLeftViewIndex + 1 + i));
                    }
                    break;
                }

            }
        }

        private boolean isEventWithinView(MotionEvent e, View child)
        {
            Rect viewRect = new Rect();
            int[] childPosition = new int[2];
            child.getLocationOnScreen(childPosition);
            int left = childPosition[0];
            int right = left + child.getWidth();
            int top = childPosition[1];
            int bottom = top + child.getHeight();
            viewRect.set(left, top, right, bottom);
            return viewRect.contains((int) e.getRawX(), (int) e.getRawY());
        }
    };

}
